Not all Dockerfile Smells are the Same: An Empirical Evaluation of Hadolint Writing Practices by Experts

Dockerfiles can be affected by bad design choices, known as Dock-erfile smells. Hadolint is currently the reference tool able to detect them, and it is widely used both by researchers and practitioners. The literature shows that these smells are commonly diffused in Dockerfiles, but it is still not clear how developers perceive them as bad practices. This paper aims to investigate the relevance of the Dockerfile smells captured by hadolint from the perspective of expert Dockerfile developers. We first perform a mining study in which we extract the change history of Dockerfiles maintained by experts to understand what smells have been more frequently introduced in their history. Next, we ran a survey in which we asked expert Dockerfile developers to evaluate Dockerfiles affected by different smells. We obtained 94 responses for 17 smells, representative of 24 Dockerfile smells. We found that experts prioritize a small part of the evaluated smells over others. Besides, they report additional bad practices not mapped as smells in any existing catalog. Thus, we propose a ranked catalog containing 26 additional Docker-file smells, which can be used as a guide for novices to understand which aspects to focus on to write good-quality Dockerfiles.CCS CONCEPTS• Software and its engineering → Software notations and tools.